Edge incremental redundancy memory structure and memory management

ABSTRACT

A system for implementing Incremental Redundancy (IR) operations in a wireless receiver includes at least one processing device, an IR processing function, and IR memory. The at least one processing device is operable to receive analog signals corresponding to a data block, to sample the analog signals to produce samples, to equalize the samples to produce soft decision bits corresponding to the data block, and to initiate IR operations. The IR processing function is operable to perform IR operations on the soft decision bits of the data block in an attempt to correctly decode the data block. The IR memory operably couples to the IR processing function, includes Type I IR memory adapted to store IR status information of the data block, and includes Type II IR memory adapted to store the data block.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 60/431,940, filed Dec. 9, 2002, and to U.S. Provisional PatentApplication Ser. No. 60/478,922, filed Jun. 16, 2003, both of which areincorporated herein by reference for all purposes.

BACKGROUND

1. Technical Field

The present invention relates generally to cellular wirelesscommunication systems; and more particularly to the processing of datacommunications received by a wireless terminal in such a cellularwireless communication system.

2. Related Art

Cellular wireless communication systems support wireless communicationservices in many populated areas of the world. While cellular wirelesscommunication systems were initially constructed to service voicecommunications, they are now called upon to support data communicationsas well. The demand for data communication services has exploded withthe acceptance and widespread use of the Internet. While datacommunications have historically been serviced via wired connections,cellular wireless users now demand that their wireless units alsosupport data communications. Many wireless subscribers now expect to beable to “surf” the Internet, access their email, and perform other datacommunication activities using their cellular phones, wireless personaldata assistants, wirelessly linked notebook computers, and/or otherwireless devices. The demand for wireless communication system datacommunications will only increase with time. Thus, cellular wirelesscommunication systems are currently being created/modified to servicethese burgeoning data communication demands.

Cellular wireless networks include a “network infrastructure” thatwirelessly communicates with wireless terminals within a respectiveservice coverage area. The network infrastructure typically includes aplurality of base stations dispersed throughout the service coveragearea, each of which supports wireless communications within a respectivecell (or set of sectors). The base stations couple to base stationcontrollers (BSCs), with each BSC serving a plurality of base stations.Each BSC couples to a mobile switching center (MSC). Each BSC alsotypically directly or indirectly couples to the Internet.

In operation, each base station communicates with a plurality ofwireless terminals operating in its cell/sectors. A BSC coupled to thebase station routes voice communications between the MSC and the servingbase station. The MSC routes the voice communication to another MSC orto the PSTN. BSCs route data communications between a servicing basestation and a packet data network that may include or couple to theInternet. Transmissions from base stations to wireless terminals arereferred to as “forward link” transmissions while transmissions fromwireless terminals to base stations are referred to as “reverse link”transmissions. The volume of data transmitted on the forward linktypically exceeds the volume of data transmitted on the reverse link.Such is the case because data users typically issue commands to requestdata from data sources, e.g., web servers, and the web servers providethe data to the wireless terminals.

Wireless links between base stations and their serviced wirelessterminals typically operate according to one (or more) of a plurality ofoperating standards. These operating standards define the manner inwhich the wireless link may be allocated, setup, serviced and torn down.One popular cellular standard is the Global System for Mobiletelecommunications (GSM) standard. The GSM standard, or simply GSM, ispredominant in Europe and is in use around the globe. While GSMoriginally serviced only voice communications, it has been modified toalso service data communications. GSM General Packet Radio Service(GPRS) operations and the Enhanced Data rates for GSM (or Global)Evolution (EDGE) operations coexist with GSM by sharing the channelbandwidth, slot structure, and slot timing of the GSM standard. The GPRSoperations and the EDGE operations may also serve as migration paths forother standards as well, e.g., IS-136 and Pacific Digital Cellular(PDC).

In order for EDGE to provide increased data rates within a 200 KHz GSMchannel, it employs a higher order modulation, 8-PSK (octal phase shiftkeying), in addition to GSM's standard Gaussian Minimum Shift Keying(GMSK) modulation. EDGE allows for nine different (autonomously andrapidly selectable) air interface formats, known as Modulation andCoding schemes (MCSs), with varying degrees of error control protection.Low MCS modes, (MCS 1-4) use GMSK (low data rate) while high MCS modes(MCS 5-9) use 8-PSK (high data rate) modulation for over the airtransmissions, depending upon the instantaneous demands of theapplication.

EDGE uses the higher order 8-PSK and the GMSK modulations and a familyof MCSs for each GSM radio channel time slot, so that each userconnection may adaptively determine the best MCS setting for theparticular radio propagation conditions and data access requirements ofthe user. In addition, the “best” air interface mode is enhanced with atechnique called incremental redundancy (IR), whereby packets aretransmitted first with initially selected MCS mode and puncturing, andthen subsequent packets are transmitted with additional redundancy usingdiffering puncturing patterns and potentially different MCS modes withina common MCS family. Rapid feedback between the base station andwireless terminal may restore the previous acceptable air interfacestate, which is presumably at an acceptable level but with minimumrequired coding and with minimum bandwidth and power drain.

The processing and memory requirements for IR service are severe.Decoding is performed for each received block and, if the decoding isnot successful, the received block must be stored until it is combinedwith a subsequently received block. This storage and combination processmay be repeated for a number of iterations. Because IR operations may bein process for a large number of blocks, the storage and indexingrequirements for IR may be significant.

Traditionally, the Radio Link Control protocol layer (RLC) wasresponsible for initiating retransmission of a block while the PhysicalLayer (PHY) was responsible for decoding. Typically, the RLC and the PHYwere implemented in separate processing devices, e.g., a first processorimplementing the RLC, e.g., RISC processor, and a second processorimplementing the PHY, e.g. DSP. Many of the operations supported by thewireless terminal justified this split in processing duties. However,when IR is implemented, the split in processing duties burdens each ofthe processors with messaging and data sharing operations simply insupport of IR. These processing and memory requirements adversely affectthe performance of wireless terminals servicing EDGE. Thus, there existsa need in the art for improved performance in supporting EDGE IR.

BRIEF SUMMARY OF THE INVENTION

In order to overcome the shortcomings of the prior devices, among othershortcomings, a system for implementing Incremental Redundancy (IR)operations in a wireless receiver includes at least one processingdevice, an IR processing function, and IR memory. The at least oneprocessing device is operable to receive analog signals corresponding toa data block, to sample the analog signals to produce samples, toequalize the samples to produce soft decision bits corresponding to thedata block, and to initiate IR operations. The IR processing function isoperable to perform IR operations on the soft decision bits of the datablock in an attempt to correctly decode the data block. The IR memoryoperably couples to the IR processing function, includes Type I IRmemory adapted to store IR status information of the data block, andincludes Type II IR memory adapted to store the data block.

The IR status information stored in Type I IR memory includesretransmission information regarding a corresponding data block sequencenumber, a Type II IR memory address for each stored data block, andModulation and Coding Scheme (MCS) mode information for each stored datablock. The type II IR memory is adapted to store soft decision bits ofthe data block, a puncturing pattern of the data block, and a signalquality indicator of the data block. Type II IR memory is adapted tostore punctured soft decision bits and/or depunctured soft decisionbits. Type II IR memory is also adapted to store either/or segmenteddata blocks and unsegmented data blocks.

In one embodiment, Type I IR memory is statically assigned while Type IIIR memory is dynamically allocated and deallocated depending upon therequirements of the IR operations. The Type I IR memory may be addressedbased upon a block sequence number of the data block.

Other features and advantages of the present invention will becomeapparent from the following detailed description of the invention madewith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram illustrating a portion of a cellular wirelesscommunication system that supports wireless terminals operatingaccording to the present invention;

FIG. 2 is a block diagram functionally illustrating a wireless terminalconstructed according to the present invention;

FIG. 3 is a block diagram illustrating in more detail the wirelessterminal of FIG. 2, with particular emphasis on the digital processingcomponents of the wireless terminal;

FIG. 4 is a block diagram illustrating the general structure of a GSMframe and the manner in which data blocks are carried by the GSM frame;

FIG. 5A is a block diagram illustrating one embodiment of the manner inwhich the Incremental Redundancy (IR) processing module interacts withthe system processor to perform IR processing according to the presentinvention;

FIG. 5B is a block diagram illustrating the interconnection of thesystem processor and the IR processing module according to variousembodiments of the present invention;

FIG. 6 is a block diagram illustrating an IR memory structure used inservicing IR operations for EDGE communications according to one aspectof the present invention;

FIGS. 7A, 7B, 7C, and 7D are block diagrams illustrating the manner inwhich RLC blocks and segmented RLC blocks are stored in Type II IRmemory according to one aspect of the present invention;

FIG. 8 is a logic diagram illustrating operation of a wireless deviceaccording to an embodiment of the present invention in performing datablock decoding operations;

FIG. 9 is a logic diagram illustrating IR operations according to anembodiment of the present invention; and

FIG. 10 is a logic diagram illustrating operation in storing data in IRmemory according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram illustrating a portion of a cellular wirelesscommunication system 100 that supports wireless terminals operatingaccording to the present invention. The cellular wireless communicationsystem 100 includes a Mobile Switching Center (MSC) 101, Serving GPRSSupport Node/Serving EDGE Support Node (SGSN/SESN) 102, base stationcontrollers (BSCs) 152 and 154, and base stations 103, 104, 105, and106. The SGSN/SESN 102 couples to the Internet 114 via a GPRS GatewaySupport Node (GGSN) 112. A conventional voice terminal 121 couples tothe PSTN 110. A Voice over Internet Protocol (VoIP) terminal 123 and apersonal computer 125 couple to the Internet 114. The MSC 101 couples tothe Public Switched Telephone Network (PSTN) 110.

Each of the base stations 103-106 services a cell/set of sectors withinwhich it supports wireless communications. Wireless links that includeboth forward link components and reverse link components supportwireless communications between the base stations and their servicedwireless terminals. These wireless links support digital datacommunications, VoIP communications, and other digital multimediacommunications. The cellular wireless communication system 100 may alsobe backward compatible in supporting analog operations as well. Thecellular wireless communication system 100 supports the Global Systemfor Mobile telecommunications (GSM) standard and also the Enhanced Datarates for GSM (or Global) Evolution (EDGE) extension thereof. Thecellular wireless communication system 100 may also support the GSMGeneral Packet Radio Service (GPRS) extension to GSM. However, thepresent invention is also applicable to other standards as well, e.g.,TDMA standards, CDMA standards, etc. In general, the teachings of thepresent invention apply to digital communications that combine AutomaticRepeat ReQuest (ARQ) operations at Layer 2, e.g., LINK/MAC layer withvariable coding/decoding operations at Layer 1 (PHY).

Wireless terminals 116, 118, 120, 122, 124, 126, 128, and 130 couple tothe cellular wireless communication system 100 via wireless links withthe base stations 103-106. As illustrated, wireless terminals mayinclude cellular telephones 116 and 118, laptop computers 120 and 122,desktop computers 124 and 126, and data terminals 128 and 130. However,the cellular wireless communication system 100 supports communicationswith other types of wireless terminals as well. As is generally known,devices such as laptop computers 120 and 122, desktop computers 124 and126, data terminals 128 and 130, and cellular telephones 116 and 118,are enabled to “surf” the Internet 114, transmit and receive datacommunications such as email, transmit and receive files, and to performother data operations. Many of these data operations have significantdownload data-rate requirements while the upload data-rate requirementsare not as severe. Some or all of the wireless terminals 116-130 aretherefore enabled to support the EDGE operating standard. These wirelessterminals 116-130 also support the GSM standard and may support the GPRSstandard. In particular, the wireless terminals 116-130 supportIncremental Redundancy (IR) operations according to the presentinvention.

FIG. 2 is a block diagram functionally illustrating a wireless terminal200 constructed according to the present invention. The wirelessterminal 200 of FIG. 2 includes an RF transceiver 202, digitalprocessing components 204, and various other components contained withina housing. The digital processing components 204 includes two mainfunctional components, a physical layer processing, speech COder/DECoder(CODEC), and baseband CODEC functional block 206 and a protocolprocessing, man-machine interface functional block 208. A Digital SignalProcessor (DSP) is the major component of the physical layer processing,speech COder/DECoder (CODEC), and baseband CODEC functional block 206while a microprocessor, e.g., Reduced Instruction Set Computing (RISC)processor, is the major component of the protocol processing,man-machine interface functional block 208. The DSP may also be referredto as a Radio Interface Processor (RIP) while the RISC processor may bereferred to as a system processor. However, these naming conventions arenot to be taken as limiting the functions of these components.

The RF transceiver 202 couples to an antenna 203, to the digitalprocessing components 204, and also to a battery 224 that powers allcomponents of the wireless terminal 200. The physical layer processing,speech COder/DECoder (CODEC), and baseband CODEC functional block 206couples to the protocol processing, man-machine interface functionalblock 208 and to a coupled microphone 226 and speaker 228. The protocolprocessing, man-machine interface functional block 208 couples to aPersonal Computing/Data Terminal Equipment interface 210, a keypad 212,a Subscriber Identification Module (SIM) port 213, a camera 214, a flashRAM 216, an SRAM 218, a LCD 220, and LED(s) 222. The camera 214 and LCD220 may support either/both still pictures and moving pictures. Thus,the wireless terminal 200 of FIG. 2 supports video services as well asaudio services via the cellular network.

FIG. 3 is a block diagram illustrating in more detail the wirelessterminal of FIG. 2, with particular emphasis on the digital processingcomponents of the wireless terminal. The digital processing components204 include a system processor 302, a baseband processor 304, and aplurality of supporting components. The supporting components include anexternal memory interface 306, Man-Machine-Interface (MMI) drivers andI/F 308, a video I/F 310, an audio I/F 312, a voice band CODEC 314,auxiliary functions 316, a modulator/demodulator 322, ROM 324, RAM 326and a plurality of processing modules. In some embodiments, themodulator/demodulator 322 is not a separate structural component withthese functions being performed internal to the baseband processor 304.Hands Free Interface (I/F) supports hands free use of the wirelessterminal.

The processing modules are also referred to herein as accelerators,co-processors, processing modules, or otherwise, and include auxiliaryfunctions 316, an equalizer 318, an encoder/decoder 320, and anIncremental Redundancy (IR) processing module 328. The interconnectionof FIG. 3 is one example of a manner in which these components may beinterconnected. Other embodiments support additional/alternatecouplings. Such coupling may be direct, indirect, and/or may be via oneor more intermediary components.

RAM and ROM service both the system processor 302 and the basebandprocessor 304. Both the system processor 302 and the baseband processor304 may couple to shared RAM 326 and ROM 324, couple to separate RAM,coupled to separate ROM, couple to multiple RAM blocks, some shared,some not shared, or may be served in a differing manner by the memory.In one particular embodiment, the system processor 302 and the basebandprocessor 304 coupled to respective separate RAMs and ROMs and alsocouple to a shared RAM that services control and data transfers betweenthe devices. The processing modules 316, 318, 320, 322, and 328 maycoupled as illustrated in FIG. 3 but may also coupled in other manners,such as the manner shown in FIGS. 5A and/or 5B in differing embodiments.

The system processor 302 services at least a portion of a servicedprotocol stack, e.g., GSM/GPRS/EDGE protocol stack. In particular thesystem processor 302 services Layer 1 (L1) operations 330, a portion ofIncremental Redundancy (IR) GSM protocol stack operations 332 (referredto as “IR control process”), Medium Access Control (MAC) operations 334,and Radio Link Control (RLC) operations 336. These operations will notbe further described herein except as how they relate to the presentinvention. The baseband processor 304 in combination with themodulator/demodulator 322, RF transceiver, equalizer 318, and/orencoder/decoder 320 service the Physical Layer (PHY) operationsperformed by the digital processing components 204.

As is known, EDGE supports both selective repeat Type I ARQ operationsand IR Type II ARQ operations for data protection. With IR operations,when a first transmitted data block is in error, a re-transmitted datablock will be sent. The re-transmitted data block may have a samecoding/puncturing pattern or a differing coding/puncturing pattern ascompared to the first data block. Soft combining of the data blocks isperformed and decoding and error checking of the combined data block(de-punctured) is then attempted. Multipleretransmission/combining/decoding operations may be attempted before theIR process terminates. IR operations are successful as compared tosimple retransmissions because coding schemes/puncturing patterns ofeach transmission are complementary to one other.

In designing a wireless device to support IR operations, a criticalissue is IR memory size and processing time. The embodiments of thepresent invention are directed to IR memory organization and also IRprocessing. One particular embodiment of the present invention supportsdownlink transmissions for up to four time slots using the IR process.The processing and memory management embodiments of the presentinvention minimize the number of data moves and maximize the usage ofthe limited IR memory size (e.g., 1 Mbits) with minimum performancedegradation.

Because IR is a joint process of ARQ in the RLC layer 336 and channelcoding in the PHY (baseband processor 304 implemented), prior devicesoften implemented IR command and control at the RLC layer. However,unlike the prior device, a wireless device of the present inventiontakes advantage of the tight relationship between the IR control process332 and the L1 process 330 to limit/avoid unnecessary interaction withthe RLC 336 during IR processing. Such efficiency is gained byperforming substantial portions of the IR operations in the IRprocessing module 328 that directly interfaces to the system processor302. The manner in which the IR control process 332 and the IRprocessing module 328 supports these operations will be described indetail with reference to FIGS. 5A though 10.

FIG. 4 is a block diagram illustrating the general structure of a GSMframe and the manner in which data blocks are carried by the GSM frame.The GSM frame is 20 ms in duration, is divided into quarter frames, eachof which includes eight time slots, time slots 0 through 7. Each timeslot is approximately 625 us in duration, includes a left side, a rightside, and a midamble. The left side and right side of an RF burst of thetime slot carry data while the midamble is a training sequence.

The RF bursts of four time slots of the GSM frame carry a segmented RLCblock, a complete RLC block, or two RLC blocks, depending upon asupported Modulation and Coding Scheme (MCS) mode. For example, datablock A is carried in slot 0 of quarter frame 1, slot 0 of quarter frame2, slot 0 of quarter frame 3, and slot 0 of quarter frame 3. Data blockA may carry a segmented RLC block, an RLC block, or two RLC blocks.Likewise, data block B is carried in slot 1 of quarter frame 1, slot 1of quarter frame 2, slot 1 of quarter frame 3, and slot 1 of quarterframe 3. The MCS mode of each set of slots, i.e., slot n of each quarterframe, for the GSM frame is consistent for the GSM frame but may varyfrom GSM frame to GSM frame. Further, the MCS mode of differing sets ofslots of the GSM frame, e.g., slot 0 of each quarter frame vs. any ofslots 1-7 of each quarter frame, may differ.

FIG. 5A is a block diagram illustrating one embodiment of the manner inwhich the IR processing module 328 interacts with the system processor302 to perform IR processing according to the present invention. Theillustrated portion of the EDGE protocol stack includes the RLC layer336, the MAC layer 334, the L1 process 330, and the IR control process332. Also shown in FIG. 5A is the IR processing module 328 and thebaseband processor 304 that manages/implements the PHY in cooperationwith the other components illustrated in FIG. 3.

The L1 process 330 supports data and control transactions by interactingbetween the PHY and the upper layers, e.g., MAC 334 layer/RLC layer 336.In performing these operations, the L1 process 330 receives data andcontrol from the MAC layer 334, operates upon the data, and passes thedata to the PHY. Likewise, the L1 process 330 receives data and controlfrom the PHY, operates upon the data and control, and passes the dataand control to the MAC 334. These operations are generally known.

According to the illustrated embodiment of the present invention, the L1process 330 intercepts IR transactions, upstream and/or downstream, anddiverts the IR transactions to the IR control process 332. The IRcontrol process 332, in turn, performs some IR operations and controlsoperation of the IR processing module 328 to process the IRtransactions. The IR control process 332 (in some cases in cooperationwith the IR processing module 328) performs IR control, IR memorymanagement, RLC/MAC header interpretation for IR combining, and trackingof the ARQ receiving state and received block bit map. With the IRcontrol process 332 performing tracking of the ARQ receiving state andreceived block bit map, no extra messages are needed between the RLClayer 336 and the L1 layer 330 for ARQ received block synchronization.The RLC layer 336 is automatically synchronized because the L1 layeronly passes correctly decoded data blocks to the RLC layer 336 (via theMAC layer 334).

In some embodiments, the IR processing module 328 acts only as a slaveto the IR control process 332 operating on the system processor 302. Insuch case the IR control process 332 directs all operations of the IRprocessing module 328 and is responsible for all memory accesses. Inother embodiments the IR processing module 328 has some/substantialcontrol over IR operations and has direct access to IR memory and tomain memory.

FIG. 5B is a block diagram illustrating the interconnection of thesystem processor 302 and the IR processing module 328 according tovarious embodiments of the present invention. Interrupt based commandcontrol may be used between the IR processing module 328 and the systemprocessor 302 using control registers 502. The system processor 302running the IR control process 332 commands the IR processing module 328to perform specific operations, e.g., header decoding, deinterleaving,data depuncturing, soft combining, data decoding, etc., via controlregisters 502. In such case the IR control process 332 running on thesystem processor 302 has control over all IR memory accesses, passesdata to the IR processing module 328, and receives data from the IRprocessing module 328.

The control registers 502 and one or more interrupt lines may be used tocouple the IR processing module 328 to the system processor 302. In suchcase, when the IR processing module 328 completes it operations, itsends an interrupt to the IR control process 332 running on the systemprocessor 302 and also writes to the control registers 502 based upon aresult of its processing. The interrupt received by the system processor302 has the highest priority (or very high priority) among otherinterrupts and therefore will be served first. In another embodiment,the IR processing module 328 and the system processor 302 communicatevia memory reads/memory writes in RAM 326, in lieu of, or in addition tocommunicating via the control registers 502.

As will be described further with reference to FIG. 6, IR memoryincludes Type I IR memory and Type II IR memory. Type I IR memory and/orType II IR memory may be implemented in RAM 326. Alternately, Type I IRmemory and/or Type II IR memory or may be implemented in a dedicated IRmemory 504. The IR processing module 328 may interface directly to RAM326, to a dedicated IR memory 504, or may interface with one or both viathe system processor 302, depending upon the embodiment. FIG. 6 is ablock diagram illustrating an IR memory structure used in servicing IRoperations for EDGE communications according to one aspect of thepresent invention. A two level data structure enables the IR processingmodule 328 or system processor 302 to write/retrieve data to/from theexternal IR memory (e.g., RAM 322, or dedicated IR memory 504)efficiently. The IR memory includes two types of data blocks: Type I IRmemory blocks and Type II IR memory blocks. Type I IR memory blocksstore rtx_flags (re-transmission flag=0, . . . , 5), MCS modes, and theaddress(es) of corresponding Type II IR memory block(s). Retransmissionflag rtx indicates a number of previous transmissions of non-segmentedRLC blocks that are stored in Type II IR memory, rtx1 indicates a numberof previous transmissions of a first segment of a segmented RLC blocksthat are stored in Type II IR memory, and rtx2 indicates a number ofprevious transmissions of a second segment of a segmented RLC block thatare stored in Type II IR memory. The modes stored in Type I IR memoryindicate particular MCS modes for respective data blocks stored in TypeII IR memory. Type II IR memory blocks hold puncturing pattern numbers,average block Signal to Interference Ratios (SIRs), padding bitinformation when MCS 8 to MCS 6 or MCS 8 to MCS 6 to MCS 3 modeswitching is performed, and soft symbol bits of the corresponding datablock.

Type II IR data memory blocks (in addition to two or more words forstorage of header information) may have a size of 156 words, 316 bytes,or another size and are dynamically allocated based upon actual storageneeds of the currently serviced operations. As will be described furtherwith reference to FIGS. 7A, 7B, 7C, and 7D, data blocks (eithersegmented RLC blocks or full RLC blocks) for all MCS modes except MCSmodes 5 and 6 can be stored in one Type II IR memory block. MCS modes 5and 6 data blocks (1248 four-bit soft data) require two Type II IRmemory blocks for storage. For each Block Sequence Number (BSN), amaximum of four (for un-segmented RLC block) or six (for segmented RLCblock) Type II IR-memory blocks are allocated. The size of Type I IRmemory block is 16 words for a given outstanding block.

In one embodiment of the present invention, a fixed allocation, e.g.,512, of Type I IR memory blocks is made to implement a streamlinedoperational process. In EDGE the BSN ranges from 0 to 2047. However forfour time-slot downlink transmissions, a maximum of 512 outstanding RLCblock BSNs are allowed. Thus, to enable quick access to the Type I IRmemory for any given received data block BSN, 512 blocks of Type I IRmemory is allocated. To obtain IR information for a received data blockBSN, the IR processing module 328 simply reads Type I data in the memory(IR_base_memory+(BSN %512)*16), where IR_base_memory is the base addressof the Type I IR memory. Based upon the Type I IR memory block read, theIR processing module 328 accesses the Type II IR memory block(s) for theadditional information and data stored therein. When fewer or more thanfour time-slot downlink transmissions are allowed, the size of the TypeI IR memory may be adjusted accordingly using the same concept.

This Flexible IR memory design allows storage of punctured and/orde-punctured data. Four Type II IR memory blocks may be associated witheach outstanding unsegmented RLC block. Each Type II IR memory blockstores soft decision bits for each previously transmitted RLC block(either punctured or de-punctured). Four Type II IR memory blocks aresufficient to encompass all puncturing patterns even with MCS modeswitching for unsegmented RLC blocks. The IR memory arrangement of theembodiments of the present invention minimize the amount of memoryrequired when only one or a few retransmissions of a data block withdifferent puncturing patterns are required. Such is the case because,without mode switching, the maximum number of puncturing patterns isthree for MCS 3 and 4 and MCS 7, 8, and 9. The de-interleaved, puncturedfour-bit blocks can be stored in one Type II IR memory block. In thiscase, only three Type II IR memory blocks will be used for eachoutstanding RLC block. For MCS 5 and 6, the de-interleaved, punctured 4bit blocks (1248 in length) can be fitted into two Type II IR memoryblocks. Thus, four Type II IR memory blocks can accommodate two RLCblocks with different puncturing pattern numbers, which is the case forMCS 5 and 6.

With mode switching, for example MCS 7 to 5, MCS 9 to 6, MCS 8 to 6, MCS5 to 7, MCS 6 to 9, MCS 6 to 8, it is possible that three Type II IRmemory blocks of a first MCS mode, e.g., MCS 7 or MCS 8 are used tostore puncturing pattern 1, 2 and 3. While switching to a lower mode,e.g., MCS 7 to MCS 5 or MCS 8 to MCS 6, there is only one Type II IRmemory block left which is not enough to store de-interleaved, puncturedMCS 5 or MCS 6 mode data. At this point, the IR storage type is switchedto store de-punctured soft decision data, 5 bits per symbols. In thiscase, the de-punctured soft decision can be equally stored in four TypeII IR memory blocks. The largest number of soft symbol data bits thatmay be stored in Type II memory are 1836 bits (612 words), 153 words perType II memory block.

The present invention not only supports mode switching but also supportsRLC block segmentation during a Temporary Block Flow (TBF). When thereis a MCS mode switch during a TBF, since the IR memory also storesheader information of the outstanding blocks that were previousreceived, combining data from different MCS modes can be easilyachieved. When an RLC block segmentation occurs (e.g. MCS 6 to MCS 3,MCS 5 to MCS 2, or MCS 4 to MCS 1), the IR processing module 328 simplyerases all copies related to this RLC block in the IR memory associatedwith the higher mode and starts storing outstanding copies with thelower modes. In this case, IR operations can still be performed forthose segmented blocks.

FIGS. 7A, 7B, 7C, and 7D are block diagrams illustrating the manner inwhich RLC blocks and segmented RLC blocks are stored in Type II IRmemory according to one aspect of the present invention. Referringparticularly to FIGS. 4 and 7A, the four slots of a GSM frame for MCS1-3 carry either a segmented RLC block, e.g., either a first portion ora second portion of the RLC block, or a complete RLC block. MCS 1-3modes use GMSK modulation with a data block having 372 soft symbol bits.Resultantly, the data block includes 93 soft symbol words that may bestored in a single 156-word Type II memory location. For MCS 1-3 modesin which segmented RLC blocks are carried, Rtx1 of Type I IR memoryindicates a number of copies of the first segment of the correspondingRLC block that are stored in Type II IR memory while rtx2 of Type I IRmemory indicates a number of copies of the second segment of thecorresponding RLC block that are stored in Type II IR memory.

Referring now to FIGS. 4 and 7B, for MCS 4, the four slots of a GSMframe carry a complete RLC block. MCS 4 mode uses GMSK modulation with adata block having 372 soft symbol bits. Resultantly, the MCS 4 datablock includes 93 soft symbol words that may be stored in a single156-word Type II memory location.

Referring to FIGS. 4 and 7C, for MCS 5-6, the four slots of a GSM framecarry a complete RLC block. MCS 5-6 uses 8 PSK modulation with each datablock including 1248 soft symbol bits/312 soft symbol words. The softsymbol bits of the MCS 5-6 data block are stored in two Type II IRmemory locations, each 156 words in size.

Referring now to FIGS. 4 and 7D, for MCS 7-9, the four slots of a GSMframe carry two complete RLC blocks. MCS 7-9 uses 8 PSK modulation andthe MCS 7-9 data block includes 612 soft symbol bits for each RLC blockit carries. Thus, the 612 soft symbol bits for the RLC block equals 153soft symbol words that may be stored in a single Type II memorylocation.

FIG. 8 is a logic diagram illustrating operation of a wireless deviceaccording to an embodiment of the present invention in performing datablock decoding operations. Operation commences with the RF transceiverawaiting an RF burst carried within a slot of a GSM quarter frame (step802). Upon receipt of the RF burst (step 804), the RF front end convertsthe RF burst to a baseband signal (step 806). Such conversion is knownand is not described further herein and typically includes estimatingthe quality of the signal, e.g., SIR. The baseband signal is thensampled. Either the baseband processor 304 or the equalizer 318 thenequalizes the baseband signal to produce soft decisions (step 808).

When a complete data block has been received (as determined at step 810)remaining operations of FIG. 8 are performed. Note that for MCS 1-3 fourslots of a GSM frame may carry either a segmented RLC block or acomplete RLC block. The IR operations of FIG. 8 beginning at step 812may be optionally implemented upon the receipt of a RLC block segment solong as a copy of the complementary segment of the RLC block is alreadystored in IR memory. Based upon information contained in the header thatis partially decoded by the baseband processor 304, the system processor302, or the IR processing module 328, the receiving devices determineswhether IR operations are required for the data block (step 812). Atstep 814, if IR operations are required, operation proceeds at step 816where non-IR data processing is performed upon the data block. From step816 operation proceeds to step 824 where data block error checking isperformed.

If IR operations are required, as was determined at step 814, operationproceeds to step 818 where the IR control process 332 running on thesystem processor 302 enacts IR operations for the data block (step 818).The IR control process 332 interacts with the IR processing module 328(step 820) to initiate/perform/complete the IR processing moduleoperations (step 822). The IR operations (step 822) are described indetail with reference to FIG. 9. Depending upon the embodiment, the IRoperations are performed jointly by the IR control process 332 and theIR processing module 328. The split in duties between these devicesdepends upon the particular embodiment.

Upon the completion of the IR processing module operations at step 822,the IR control process 302 determines whether the IR operations weresuccessful via error checking of the decoded RLC block (step 824). Errorchecking performed at step 824 is done using a cyclical redundancycheck, for example. If the IR operations were successful and no errorsare found in the decoded RLC block the data is passed to the MAC 334/RLC336 layers of the protocol stack operating on the system processor 302.The IR control process 332 operating on the system processor, incooperation with the IR processing module 328, in some embodimentsclears IR memory corresponding to the BSN, if required (step 828).Clearing memory corresponding to the BSN of the data block includesreleasing all Type II IR memory and also overwriting any data in Type IIR memory for the BSN with null data, e.g., rtx=0, rtx=0, rtx2=0. Ofcourse, if the data block operated upon was the first transmission ofthe RLC block then IR memory has no stored contents and memory clearingis not required.

If decoding of the data block results in errors, as determined at step824, the IR control process 332, either by itself or in combination withthe IR processing module 328, stores the data block in IR memorycorresponding to the BSN of the data block (step 826). This operationwill be described further with reference to FIG. 10.

FIG. 9 is a logic diagram illustrating IR operations according to anembodiment of the present invention. The operations of FIG. 9 arereferred to as being performed by the IR processing module 328 and/orthe IR control process 332 implemented on the system processor 302. Theresponsibility for these operations described with reference to FIG. 9is for the described embodiment only. In other embodiments the split inIR processing duties may differ without departing from the scope of thepresent invention.

Operation commences with the IR processing module 328 receiving softdecisions corresponding to the data block, i.e., either RLC block orsegmented RLC block (step 902). As was previously described withreference to FIGS. 3, 5A and 5B, the IR processing module 328 mayreceive the soft decisions of the data block via a memory read andwrite, via control registers 502, directly from the IR control process332 operating on the system processor 302, or via another particularoperation. The IR module 328 (or IR control process 332) then decodesthe soft decisions of the header to extract information regarding thedata block (step 904). The decoded header will include the BSN of thedata block, the MCS mode of the data block, the puncturing pattern ofthe data block, whether the data block carries a complete RLC block or asegmented RLC block, and additional information that may be required forIR operations. The data is then deinterleaved (step 906). In otherembodiments the deinterleaving may be done earlier or later in the IRprocess but in all cases prior to depuncturing, soft bit combining (ifrequired), and decoding.

Next, the IR processing module 328 (or IR control process 332)determines whether the data block is an initial transmission of the RLCblock or whether the data block is a retransmission of the RLC block(step 908). Alternately, the IR processing module 328 may pass thedecoded information back to the IR control process 332, which makes thedetermination regarding whether the data burst is a retransmission. Thisdetermination may be made by reading rtx, rtx 1, and rtx2 from the TypeI IR memory for the block sequence number of the data block, e.g., RLCblock BSN. If this is a first transmission of the data block, e.g.,rtx=0, then operation proceeds to step 910. If not, the data block is aretransmission of a previously transmitted data block, e.g., rtx>0 andoperation proceeds to step 916.

For a first transmission of the data block, the IR processing module 328depunctures the deinterleaved data block (step 910). In depuncturing thedata block the IR processing module converts the soft symbols fromfour-bit data to five-bit data. Because depuncturing requires thatnon-received data be inserted into a bit sequence, which is essentiallydata with no reliability. Soft decisions of the received data block thatare represented in the four-bit format as produced by the equalizationprocess have a reliability or confidence factor included therewith. Forexample, a very confident soft decision for a binary 1 may berepresented as a 1111 while a very unconfident soft decision for abinary 1 may be represented as a 1000. Likewise, a very confident binary0 soft decision may be represented as 0111, while a very unconfidentbinary 0 soft decision may be represented as 0000. Alternately, a veryconfident binary 0 soft decision may be referenced as 0000, while a veryunconfident binary 0 soft decision may be represented as 0111. In eithercase, in the depuncturing operation wherein non-received data isinserted, the inserted soft decision bits have a lowest confidence thatmay be represented. The four-bit data is expanded based upon itsconfidence level such that a confident binary one, represented asfour-bit nibble 1111 may be extended to a very confident five-bitsequence of 11111 or 11110, for example.

After the depuncturing process is complete the IR processing module 328decodes the five-bit data (step 912) and then returns the decoded resultto the IR control process 332 (step 914). From step 914 operationreturns to step 824 of FIG. 8.

When the data block considered at step 908 is not the first transmissionof the data block, e.g., rtx>0, rtx1>0, or rtx2>0, operation proceedsfrom step 908 to step 916 where the quality of the currently receiveddata block is considered. If the IR module 328 (or IR control process332) determines that the quality of the data received is no better thanthe quality of the data it has already stored in IR memory, no decodingis performed for the received data block and operation ends withouteither attempting decoding on the data block or storing the currentlyreceived data block. The SIR associated with the received data or otherquality indications, such as the relative certainty of the softdecisions, may be used as a threshold to determine whether decodingshould be attempted.

If the quality of the currently received data block justifies anadditional decoding for the data block (or combined data block createdtherewith), as determined at step 916, the IR processing module 328 orIR control process 332 operation proceeds to step 918. At step 918, theIR control process 332 or IR processing module 328, based upon theinformation in the decoded header and information contained in the TypeI IR memory, determines whether the MCS mode of the received data blockis incompatible with previously stored data block(s).

As is known, the MCS modes of the EDGE standard include a number offamilies. A first family includes MCS 9, MCS 8, MCS 6, and MCS 3. Asecond family includes MCS 7, MCS 5, and MCS 2. Finally, a third familyincludes MCS 4 and MCS 1. During normal operations, copies of aparticular data block be transmitted using MCS modes within a common MCSfamily so that the retransmitted copies of the data block may becombined to produce combined data blocks that are more likely to becorrectly decoded. Thus, for example, if an MCS 9 mode is used for thefirst transmission, an MCS 6 mode with puncturing pattern 1 is used fora second transmission, and an MCS 6 mode with puncturing pattern 2 isused for a third transmission, all transmitted data block copies may becombined.

Not all MCS modes or transmissions therein are compatible. Further, thesize of the Type II IR memory for the particular BSN may not be largeenough to store all compatible transmissions. Further, initialtransmissions may include complete RLC blocks and subsequenttransmissions may include segmented RLC blocks. For example, if a firsttransmission occurs using MCS 9, a second using MCS 6, and a third usingMCS 3, the MCS 9 and MCS 6 data will be discarded upon receipt of theMCS 3 data. Further, if the initial transmission includes split RLCblocks, e.g., MCS 3, a subsequent transmission in the same family thatdoes not segment data blocks, e.g., MCS 6, will be incompatible. Thus,in such case, the stored data for the prior MCS 3 transmissions would bedeleted. If the currently received data block is of an MCS mode that isincompatible with stored data blocks, previously stored data in IRmemory is discarded by clearing the Type I IR memory corresponding tothe BSN of the data block (step 920). Then, the currently received datablock is processed as if it was the first transmission for the datablock.

When the retransmitted data block is of a compatible MCS mode, asdetermined at step 918, four-bit combining with stored data is performedfor the received data if possible (step 922). The operations forfour-bit combining are performed when a stored data block and thereceived data block (with the same BSN) have the same MCS mode and thesame puncturing pattern. Four-bit combining may be done based upon thequality of the respective bursts, e.g., SIR, or other considerations inan attempt to produce a signal having a superior quality as compared tothe separate transmissions.

After the four-bit combining has been performed, if possible, four-bitdata is depunctured to produce five-bit data (step 924). After thedepuncturing is performed, it is determined whether the five-bit datamay be combined with one or more stored copies of the data block (step926). If a stored copy of the data block may be combined with thecurrent data block, the stored data block is retrieved (step 928). Ifthe stored data block is in a four-bit format, it is depunctured (step928 also). If the stored data block is stored in a five-bit format,depuncturing is not required. The retrieved data block, in a five-bitformat, is then combined with the current five-bit data block in afive-bit combining operation (step 930). Operation returns to step 926where additional stored data is considered for five-bit combining. Ifadditional stored data block(s) are available for five-bit combining,steps 928 and 930 are repeated for the additional data block(s). Whenall data blocks has been five-bit combined, as determined at step 926,operation proceeds to step 912 wherein decoding is performed and then tostep 914 where the decoded result is returned.

FIG. 10 is a logic diagram illustrating operation in storing data in IRmemory according to an embodiment of the present invention. Data may bestored in Type II IR memory in either a four-bit format or a five-bitformat. While a four-bit format for storage is preferred to minimize thesize of the Type II IR memory no data is lost when storing the data in afive-bit format. As the reader should appreciate, in IR operations anumber of copies of a data block may be received, each having adifferent MCS mode and/or a different puncturing pattern. After a numberof data block receipts without a successful decode, the amount of datarequiring storage may be large. According to one aspect of the presentinvention the size of the IR memory is limited for each BSN based uponpractical memory limitations. To address this limitation, the IRoperations of the present invention support the storage of a combinedresult (or a plurality of received data blocks) that is in a five-bitformat.

Referring particularly to FIG. 10, when storage of a data block isrequired, the IR control process 332 or IR processing module 328determines whether Type II IR memory is available for the BSN (step1002). If Type II IR memory is available for the BSN the IR controlprocess 332 or IR processing module 328 stores the data block in a fourbit format in Type II IR memory corresponding to the BSN (step 1004).The IR control process 332 or IR processing module 328 then updates theType I IR memory for the BSN according to the data stored, i.e., updatertx, rtx1, or rtx2, mode (for the stored copy), MCS mode (for the storedcopy), and Type II IR memory address (for the stored copy) (step 1006).

If no additional Type II IR memory is available for the BSN (asdetermined at step 1002), the IR control process 332 clears all Type IIIR memory locations for the BSN, or all except for the Type II IR memorythat will be used in the current storage operation (step 1008). The IRcontrol process 332 then stores the combined five-bit result in Type IIIR memory (step 1010) and updates Type I IR memory for the BSNaccordingly (step 1012).

The foregoing description of a preferred embodiment of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings or may be acquired from practice of the invention. Theembodiment was chosen and described in order to explain the principlesof the invention and its practical application to enable one skilled inthe art to utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the claimsappended hereto, and their equivalents.

1. A system for implementing Incremental Redundancy (IR) operations in awireless receiver comprising: at least one processing device that isoperable to receive analog signals corresponding to a data block, tosample the analog signals to produce samples, to equalize the samples toproduce soft decision bits of the data block, and to initiate IRoperations, the at least one processing device operable to perform asubstantial portion of Physical (PHY) layer operations and the MediaAccess Control (MAC) layer operations of the system, to investigatewhether IR operations are required for the soft decision bits of thedata block, and to initiate IR operations based upon the investigation;an IR processing function that is operable to perform IR operations onthe soft decision bits of the data block based upon a direction from theat least one processing device and in an attempt to correctly decode thedata block; and IR memory operably coupled to the IR processingfunction, the IR memory including Type I IR memory adapted to store IRstatus information of the data block and Type II IR memory adapted tostore the data block.
 2. The system of claim 1, wherein the IR statusinformation stored in Type I IR memory stores retransmission informationregarding a corresponding data block sequence number, a Type II IRmemory address for each stored data block, and Modulation and CodingScheme (MCS) mode information for each stored data block.
 3. The systemof claim 1, wherein the Type II IR memory is adapted to store softdecision bits of the data block, a puncturing pattern of the data block,and a signal quality indicator of the data block.
 4. The system of claim3, wherein Type II IR memory is adapted to store either punctured softdecision bits or depunctured soft decision bits.
 5. The system of claim4, wherein punctured soft decision bits are represented by a firstnumber of soft decision bits per symbol and depunctured soft decisionbits are represented by a second number of soft decision bits persymbol, wherein the second number is greater than the first number. 6.The system of claim 4, wherein the punctured soft decision bits arerepresented by four soft decision bits per symbol and the depuncturedsoft decision bits are represented by five soft decision bits persymbol.
 7. The system of claim 1, wherein the IR memory is adapted tostore both segmented data blocks and unsegmented data blocks.
 8. Thesystem of claim 1, wherein: Type I IR memory is statically assigned; andType II IR memory is dynamically allocated and deallocated dependingupon the requirements of the IR operations.
 9. The system of claim 1,wherein Type I IR memory is addressed based upon a block sequence numberof the data block.
 10. The system of claim 1, wherein at least a portionof the IR processing function comprises an IR processing module distinctfrom the at least one processing device.
 11. The system of claim 1,wherein the at least one processing device comprises a system processorand a baseband processor.
 12. The system of claim 1, wherein the IRprocessing function and the IR memory support Modulation and CodingScheme (MCS) modes of the GSM EDGE standardized protocol.
 13. The systemof claim 1, wherein the IR memory is operable to store soft decisionbits formed by combining soft decision bits of multiple data blocks. 14.A method for servicing Incremental Redundancy (IR) operations in awireless receiver comprising: by at least one processing device that isoperable to execute a substantial portion of Physical (PHY) layeroperations and a substantial portion of Media Access Control (MAC) layeroperations of the wireless receiver: performing PHY layer operationsincluding: receiving an analog signal corresponding to a data block;sampling the analog signal to produce samples; and equalizing thesamples to produce soft decision bits of the data block; determiningthat IR operations are required for the soft decision bits of the datablock; and performing IR operations on the soft decision bits of thedata block, including decoding the soft decision bits of the data block;failing to correctly decode the data block; storing IR statusinformation regarding the data block in Type I IR memory; allocatingType II IR memory for the data block; storing an address of theallocated Type II IR memory in Type I IR memory; and storing at least aportion of the soft decision bits of the data block in the allocatedType II IR memory.
 15. The method of claim 14, further comprising:receiving a second data block; determining that a Modulation and CodingScheme (MCS) mode of the second data block is compatible with a MCS modeof the data block; retrieving soft decision bits of the data block fromthe allocated Type II IR memory; combining soft decision bits of thedata block with soft decision bits of the second data block to producecombined soft decision bits; and decoding the combined soft decisionbits.
 16. The method of claim 15, wherein combining soft decision bitsof the data block with soft decision bits of the second data block toproduce combined soft decision bits comprises combining punctured softdata bits of the data block with punctured soft data bits of the seconddata block.
 17. The method of claim 15, wherein combining soft decisionbits of the data block with soft decision bits of the second data blockto produce combined soft decision bits comprises combining depuncturedsoft data bits of the data block with depunctured soft data bits of thesecond data block.
 18. The method of claim 14, wherein: each symbol ofthe data block is represented by four soft decision bits; and eachsymbol of the data block is represented by five depunctured softdecision bits.
 19. The method of claim 14, further comprising addressingType I IR memory addressed based upon a block sequence number of thedata block.